Removing wax and asphaltic constituents from oil



' unire s'rn'rss PA'rsN'r] aanrovmo. WAX AND AsPnALrlo coNsTl'r- UENTs raoM on.

James H. Grahame, Mount Vernon, and William L. Douthett, Jackson Heights, N. Y., assignors to The Texas Company, New York, N. Y., a corporation ot'De/lawarc Application N ovember 24, 1936, Serial Nin-112,470

' 5 claims. (ci. 19e- 18) e v This invention relates to a method of removprecipitate composed of wax and asphaltic maing wax and asphaltic constituents from hydroterial by iiltration.

carbon oil, and particularly to the removal of The dewaxed solution may still contain subsuch constituents from residual Wax-bearing stantial amounts of asphaltic material, and in mineral oil` r which case it is advantageously subjected to set- 5 'I'he invention contemplates a method of 'retling at a temperature of around125 to 150 F. lining Wax-bearing oil containing relatively soft to -remove any remaining asphaitic material as and relatively hard asphaltic constituents wherea precipitate. l in the soft asphaltic constituents are removed, Instead oi propane, Voth'er liquefied normally and the oil isthen dewaxed in the presence of all gaseous hydrocarbons may be employed, such as l0 or a portion of the relatively hard asphaltic con- ,ethane, propylene, butane, etc., or a light petrolstituents. These hard asphaltic constituents are cum fraction composed of a mixture of such hyremoved along with the wax and are of such a drocarbons.

nature that they aid in the separation of the wax It is also contemplated that the dewaxing step l5 from the oil, particularly where such separation may be carried out in the presence of a suitable l5 is eiected by filtration. r waxantisolvent liquid, such as acetone, methyl An object of the invention is to remove the soft .ethyl ketone, liquid sulphur dioxide, benzalde- I asphalt from the wax-bearingoil prior to de- .hyde. Theanti-solvent liquid maybe added to waxing,` while takingv advantage of the lterfaid the solution of wax-bearing oil and lightpetroproperties of the hard asphaltic constituents of,` leum solvent subsequent to the removal oi the 20 vthe oilin the subsequent dewaxing step. The soft soft asphalt fraction.

a'sphaltic material contained in the oil may com- Where it isdesired to subject the dewaxedoil prise a substantial proportion thereof, and since to-a further solvent refining step for the removal this material must be eliminated sooner or later, of low viscosity index constituents, advantage it is desirable to eliminate it prior to the dewaxing A.may be taken of the selective action of the wax 25 step so as to thereby increase the-capacity of'ex- Aanti-solvent liquid. That portion of the antiisting dewaxing equipment, and thus vaiord more solvent liquid remaining in the dewaxed solueconomical, operation. n tion may comprisefa. portion of the selective sol- In carrying out the process of thisinvention, vent mixture used in the subsequent solventexa solvent, such as propane, is mixed with a. waxtraction of oil. 30 bearing residual oil such as derived from Mid- Heavy residual wax-bearing fractions. such as Continent crude for example. The ratio of pro. derived `from Mid-Continent crude," contain large paneuto oil is such that the asphaltic material amounts of asphaltic and resinous material in precipitated from the mixture at a temperature addition to the wax.. For example, ,such a residof around 80? to 100 F. comprises mainly the asuum Vmay contain around 12% lto 18% by, vol- 35 phaltene type of constituent which tends to sepumev of paramn wax, and around 30% to 40% arate in hard granular form. The soft and resinby volume of tarry material. l ous type of asphaltic material comprising, in 'I'his proportion of tar represents the portion many cases, the b'ulk of the asphalt content of of the oil removed in the acid layer obtained 40 the oil remains in solution along with the oil and when about five parts of the residuum, diluted 40 wax. This solution is removed and modified to v with an equal quantity of Stoddard solvent-are effect removal of the soft asphaltic and resinous agitated with about one part of 932% sulphuric material. acid. This tarry material comprises constituents4 Modication of the solution kmay be accomwhich are of the character of aspl'ialtenes,l and n plished by the addition of a further quantity of also constituents which are of a resinous nature. 45

propane, andsubjecting the resulting mixture to VThe asphaltenes' are less soluble in propane settling at a. temperature of around 125 to 150 than the resinous material; that is, both the asl F. Under these conditions, the soft asphaltic phaltenes and resins will precipitate froma mix# and resinous material isfremoved. ture of propane and-oil containing them at a To the remaining solution is addednthe precipitemperature of130 to 150 F. But at lower 50 tate containing hard granular asphalt removed temperatures. while the asphaltenes will prein the preliminary operation. This mixture is cipitate from the same mixture, the resins will then subjected to dewaxing in the conventional precipitate in correspondingly smallerf'am'ount. manner, involving chilling' to a temperature of' In other words, the lower the temperature, the

0 F. to 40 F. and 'removing the resulting more soluble the resinous material is in the sol- 56- vent. At low temperatures, such as prevail during dewaxing, practically all of the resinous type of asphaltic material may. remain in solution.

It has been found that the asphaltene type of material which separates from a mixture of about one Vpart of residuum and three to four parts of propane, at a temperature of around 90 F. and below, imparts free-filtering .characteristics to the wax precipitated from such oil; that is, asphaltenes separate from such a mixture in a relatively dry,` hard, granular form, and thus provide an effective, solid, inert filter-aid material for aiding in the filtration of the solidified wax from a mixture of wax-bearing oil and sol-1 vent.

When the wax is precipitated from the waxbearing solution in the presence of these insoluble asphaltic constituents, the resulting precipitate is of a hard granular nature, and such that it can be removed by filtration at comparatively rapid rates. For example, the filtration rates may range from ten to a hundred times as rapid as those prevailing in the case where these asphaltic constituents are not present in the filter cake.

By proceeding in accordance with the process of this invention, the above mentioned hard granular asphaltene constituents desired as a filter-aid are segregated in a preliminary operation. Following this, the remainder of the asphaltic and resinous material comprising soft asphalt is removed, and thereafter the hard granular material preliminarily precipitated is mixed back with the Wax-bearing solution from fwhich the soft asphalt has been removed. In

this way, the softasphalt is eliminated prior to dewaxing, and the subsequent dewaxing is effectedin the presence of the hard granular asv40- When dewaxing a -lVIid-Continent type of replialtic constituents originally present in the oil.

` siduum, satisfactory filtration rates have been jobtained when the wax filter cake comprised about'j one part of Aasphaltic material to about 'three' parts of Wax. The asphaltic material thus present in the Wax cake comprised about 2% to 5% of the total asphaltic .matter contained Aabout four parts of propane to one part of oil.

The resulting mixture is then conducted to a settler 2 maintained at a temperature of around 80 to 100 F. The asphalticmaterial precipitated in this settler is withdrawn -in the form of a slurry from the bottom thereof through a pipe 3 to which reference will be made later.

The solution of oil and propane in the upper portion of the settler 2 is withdrawn through the heating coil 4, and conducted to a settler 5. If necessary, a further quantity of propane may be mixed with the solution prior to passage through the heating coil 4. The solution is maintained in the settler 5 at a temperature of around 130 to 150 F. to cause precipitation of the soft and remaining asphaltic constituents of the oil. The precipitated matter is withdrawn from this settler through a' pipe 6 towhich reference will be made later.

The solution accumulating in the upper por- .'tion of the settler 5 is drawn off and conducted to a mixer 'l wherein it is mixed with the precipitated material removed from the settler 2 through the pipe 3 previously referred to. An additional quantity of propane may also be added to the s'olution at this point, if desired. From the mixer 1, the mixture is conducted through a heater 8 and a chiller 9. In the heater 8 the mixture may be ,heated to a temperature of around 150 to 190 F. prior to introduc-tion to the chiller. vWhere it is desired to omit the heating step, the mixture may bypass the heater and be conducted directly to the chiller 9.

The heating step is desirable where the waxbearing solution contains either an artificial or a naturally-occurring Wax crystal modifying substance. It has been found that when the solution does contain such substance, heating to an elevated temperature such as that mentioned, prior to chilling, promotes the modifying action of the substance upon the structure of the wax crystals precipitated from the solution during the subsequent chilling.

Heavy residual lubricating oil stocks usually contain naturally-occurring resinous constituents which possess the ability to modify the wax crystal structure. times deficient in this respect, and therefore it is particularly desirable to add an articial modifying substance, such as crude Montan wax, aluminum stearate, or a mixture thereof. In such case, the modifying substance may be incorporated in the wax-bearing solution prior to introduction of the solution to the mixer 1. The chiller 9 is-advantageously of the evaporative type-wherein chilling is effected by vaporizing surplus propane from the wax-bearing solution undergoing chilling. On the other hand, the chiller may be of the more conventional type wherein the wax-bearing solution is chilled by passage in indirectheat exchange relationship with a refrigerant.

From the chiller 9, the solution is conducted at a temperature of around to 50 F. to a filter I0 to eiect removal of the wax. y

The resulting dewaxed filtrate is conducted through a heating coil II, and from there to a settler I2 wherein any remaining asphaltic matter is precipitated.v 'Ihis may be accomplished by maintaining the settler at a temperature in the range 125 to 130 F., either with or without the addition of a further quantity of propane. The precipitated material, mixed with some propane, is withdrawn from the 'bottom of this settler and conducted to a stripper I3 to remove the propane from the asphalt.

The solution accumulating in the top ofthe settler I2 is conducted to a stripper Il wherein the propane is removed to produce a dewaxed deasphalted oil.

The soft asphalt which is withdrawn from the bottom of the settler throughthe pipe 6 is conducted to a washer I5 wherein it may be washed with a further quantity of propane. This washer may be maintained at a temperature of 130 to 150 F., or at a temperature slightly above that maintained in the settler 5.

The resulting precipitated material is drawn off to a stripper I6 wherein the propane is removed, leaving the soft asphaltic material.-

The solution collecting in the upper portion o1' the washer I5 may be withdrawn directly to a stripper I1 `to effect removal of the propane and produce an oil product of intermediate character.

Less viscous oils are some- 0n the other hand, this solution may be conducted to the mixer 1, previously referred to, and therein mixed with the main body of solution for dewaxing.

While certain temperatures and temperature ranges have been specied with respect to the several operations described in the foregoing statement and ldescription of the invention, it is contemplated that other temperature conditions may be employed, depending upon the nature of-the oil undergoing treatment, and also upon the de-- With respect to the second step, wherein the` soft asphaltic constituents are removed, the temperatures may range from 125 to 180 F., for example. Obviously, many modifications and variation of the invention, as hereinbefore set forth, may

` be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims;

We claim: n

1. The method of removing asphalt and wax from residual wax-bearing lubricating oil containing a relatively large amount of bothfsoft and hard asphalt comprising mixing the oil with a liquefied normally gaseous hydrocarbon in such proportion that at a temperature of around 80 to 100 F., a small amount of hard granular asphalt is precipitated, maintaining the lmixture at such temperature to precipitate a slurry of hard granular asphalt amounting to about 2% to 5% of the asphaltic content of theresiduum and mixed with some solvent, removing the slurry, adding further solvent tothe remaining solution, maintaining the solution at a slightly higher temperature. suilicient to precipitate remaining asphalti'c constituents, removing the asphaltio constituents so precipitated, thereby leaving a deasphalted solution, mixing the deasphalted solution with said slurry containing hard granular asphalt, chilling the mixture to a temperature of 0 F. and below to precipitate wax, and filtering the cold mixture to remove the wax in the presence of `said hard granular asphalt.

2. The method according t'o claim 1 in which a small amount of a wax crystal regulator is incorporated in the mixture of oil,'solvent and hard granular asphalt.

3. The method of removing asphalt and -wax from residual wax-bearing lubricating oil containing a relatively large amount of both' soft and hard asphalt comprising mixing the oil with a liquefied normally gaseous hydrocarbon in such proportion that at al temperature of around to F. a small amount oi hardgranular asphalt is precipitated, maintaining the mixture at such temperature to precipitate a slurry of hard l granular asphalt amounting to about 2% to 5% of the asphaltic content of the residuum and mixed with some solvent, removing the slurry, adding further solvent to the remaining solution, maintaining the solution at a slightly higher temperature sufdcient to precipitate remaining asvphaltic constituents, removing the asphaltic constituents so precipitated thereby leaving a deasphalted solution, mixing the deasphalted solution with said slurry containing hard granular'asphalt, incorporating in said mixture a small amount of a wax crystal regulator, heating the resulting mixture to atemperature in' the range 150 to 190 F., chilling the mixture to a temperature of 0 F.v and below to precipitate wax, and filtering the cold mixture to remove the wax in the presence of said hard granular asphalt.

4. The methodof removing asphalt and wax from residual wax-bearing lubricating oil `containing a relatively large amount of both soft and hard asphalt comprising mixing the oil with a liqueiied normally gaseous hydrocarbon in such proportion that at a temperature of around 80 to 100 F., a small amount of hard granular asphalt is precipitated, while the bulk of the asphalt is retained in solution, precipitating from the mixture a small amount of hard granular asphalt in the form of a slurry mixed with some solvent, removing the slurry, maintaining the remaining mixture at a temperatureof around to- F., and while at such temperature precipitating remaining asphalticconstituents, removing the asphaltic constituents so precipitated, thereby producing a deasphalted solution,

mixing the deasphalted solution with said slurry containing hard granularasphalt, chilling this ,mixture to` precipitate wax and ltering the chilled mixture to remove the wax in Vthe presence of said hard granular asphalt.

5. The method 'of removing asphalt and wax from-residual wax-bearing lubricating oil containing arelatlvely large anount of both soft and hard asphalt comprising mixing the oil with- .a liquefied normally gaseous hydrocarbon, maintaining. the mixture at a temperature of around 80 to 100 F. sufllcientto precipitate a slurry of hard granular asphalt amounting to about 2 -to 5% o! the asphaltic content of the residuum and mixed with some solvent, removing the slurry, maintaining the remaining solution at a temperature of around 130 F. and above suiiiclent to vprecipitate remaining asphaltic constituents, removing the asphaitic constituents so precipitated,

thereby producing a deasphalted solution, mixing the deasphalted solution with said slurry containing hard granular asphalt, chilling the mixture to precipitate wax, and filtering the cold mixture to lremove the wax in the presence of said hard granular asphalt.

.JAMES H. GRAHAME. WILLIAM L. DOUTHETI. 

